Control apparatus, control method, and medical support arm apparatus

ABSTRACT

[Solution] There is provided a control apparatus configured to execute a current tracking control on a basis of a measurement value of a torque sensor of an actuator provided in at least one of multiple joint sections included in an arm section of a medical support arm apparatus, the current tracking control causing a motor of the actuator to output torque by which a position and an attitude of the arm section are maintained, and switch a first state in which the motor is driven in accordance with a predetermined control method, and a second state in which the joint section is locked using a brake of the actuator.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/745,173, filed Jan. 16, 2018, which is based on PCT filingPCT/JP2016/066001, filed May 31, 2016, which claims priority to JP2015-154100, filed Aug. 4, 2015, the entire contents of each areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a control apparatus, a control method,and a medical support arm apparatus.

BACKGROUND ART

Recently, in the medical field, support arm apparatus are being used tosupport surgeries. For example, a method is proposed in which anobservation unit such as a camera for observing an operative site isprovided on the front end of an arm section of a support arm apparatus,and the surgeon performs surgery while viewing an image taken by theobservation unit. Alternatively, there is also proposed a method ofcausing a support arm apparatus to perform work that has been donemanually in the past, such as by providing a treatment tool such asforceps on a front end of an arm section, and using the treatment tool.

Herein, some support arm apparatus are provided with a motor and a brakein each joint section, and are configured to drive the arm section withthe motor. Additionally, when locking the position and the attitude ofthe arm section, some support arm apparatus are configured to cause thebrake to engage while also cutting off the supply of power to the motor.In such a support arm apparatus, when switching from a state in whichthe position and the attitude of the arm section are locked by the braketo a state in which the brake is released and the arm section isdrivable by the motor, there is concern that the arm section could movedue to its own weight.

To prevent this, for example, Patent Literature 1 discloses a technologyin which, when releasing a brake and resuming a supply of power to amotor, a compensation amount for compensating the falling of the armsection is added to or subtracted from a command value of the current.

CITATION LIST Patent Literature

Patent Literature 1: JP H5-138583A

DISCLOSURE OF INVENTION Technical Problem

Herein, with the technology described in Patent Literature 1, aparameter such as a falling amount corresponding to the configuration ofthe arm section and the attitude of the arm section is computed inadvance, and the above compensation amount is calculated on the basis ofthe parameter. Consequently, in a case in which the surroundingenvironment changes, such as a case in which the temperature changes,for example, effectively suppressing the falling of the arm section isthought to be difficult.

In light of the above circumstances, in an arm section, when switchingbetween a state in which the position and the attitude are locked by abrake, and a state in which the arm section is drivable by a motor,there is demand for technology capable of further suppression of themovement of the arm section. Particularly, in a medical support armapparatus, even tiny movements of the arm section can possibly affect amedical procedure. Consequently, from the perspective of safety, furthersuppression of the movement of the arm section when switching states isimportant.

Accordingly, the present disclosure proposes a new and improved controlapparatus, control method, and medical support arm apparatus capable offurther suppression of the movement amount of an arm section whenswitching states.

Solution to Problem

According to the present disclosure, there is provided a controlapparatus configured to execute a current tracking control on a basis ofa measurement value of a torque sensor of an actuator provided in atleast one of multiple joint sections included in an arm section of amedical support arm apparatus, the current tracking control causing amotor of the actuator to output torque by which a position and anattitude of the arm section are maintained, and switch a first state inwhich the motor is driven in accordance with a predetermined controlmethod, and a second state in which the joint section is locked using abrake of the actuator.

In addition, according to the present disclosure, there is provided acontrol method including: executing a current tracking control on abasis of a measurement value of a torque sensor of an actuator providedin at least one of multiple joint sections included in an arm section ofa medical support arm apparatus, the current tracking control causing amotor of the actuator to output torque by which a position and anattitude of the arm section are maintained; and switching a first statein which the motor is driven in accordance with a predetermined controlmethod, and a second state in which the joint section is locked using abrake of the actuator.

In addition, according to the present disclosure, there is provided amedical support arm apparatus including: an arm section provided amedical tool on a front end; and a control apparatus configured tocontrol an operation of the arm section. The control apparatus isconfigured to execute a current tracking control on a basis of ameasurement value of a torque sensor of an actuator provided in at leastone of multiple joint sections included in the arm section, the currenttracking control causing a motor of the actuator to output torque bywhich a position and an attitude of the arm section are maintained, andswitch a first state in which the motor is driven in accordance with apredetermined control method, and a second state in which the jointsection is locked using a brake of the actuator.

According to the present disclosure, in a joint section of an armsection, when switching between a state in which the joint section isdriven by a motor in accordance with a regular control method, and astate in which the joint section is locked by a brake, the states areswitched after conducting a current tracking control. Also, in thecurrent tracking control, the driving of the motor is controlled suchthat the position and the attitude of the arm section may be maintainedwhen the states are switched. Consequently, in the instant when thestates are switched, the position and the attitude of the arm sectionare maintained by the current tracking control. Thus, changes in theposition and the attitude of the arm section attendant on the switchingof states can be suppressed.

Advantageous Effects of Invention

According to the present disclosure as described above, furthersuppression of the movement amount of an arm section when switchingstates becomes possible. Note that the effects described above are notnecessarily limited, and along with or instead of the effects, anyeffect that is desired to be introduced in the present specification orother effects that can be expected from the present specification may beexhibited.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an overall configuration of a supportarm apparatus according to a first embodiment.

FIG. 2 is an exploded perspective view illustrating an exemplaryconfiguration of an actuator provided in each joint section of thesupport arm apparatus according to the first embodiment.

FIG. 3 is a block diagram illustrating a system configuration of thesupport arm apparatus according to the first embodiment.

FIG. 4 is a flowchart illustrating an example of a processing procedureof a brake release control according to the first embodiment.

FIG. 5 is a flowchart illustrating an example of a processing procedureof a brake engagement control according to the first embodiment.

FIG. 6 is a block diagram illustrating an example of a functionalconfiguration of a motor controller according to the first embodiment.

FIG. 7 is a flowchart illustrating an example of a processing procedureof a brake release control according to a second embodiment.

FIG. 8 is a flowchart illustrating an example of a processing procedureof a brake engagement control according to the second embodiment.

FIG. 9 is a block diagram illustrating an example of a functionalconfiguration of a motor controller according to the second embodiment.

FIG. 10 is a sequence diagram illustrating a processing procedure for amodification in which the brake release control or the brake engagementcontrol in each actuator is conducted at a different timing.

FIG. 11 is a sequence diagram illustrating an example of a processingprocedure for a modification in which the brake release control or thebrake engagement control in each actuator is conducted at a differenttiming.

FIG. 12 is a graph illustrating change in a rotational angle of anoutput shaft of an actuator when the brake release control is executed.

FIG. 13 is a graph illustrating change in a driving current of a motorof an actuator when the brake release control is executed.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, (a) preferred embodiment(s) of the present disclosure willbe described in detail with reference to the appended drawings. Notethat, in this specification and the drawings, elements that havesubstantially the same function and structure are denoted with the samereference signs, and repeated explanation is omitted.

Hereinafter, the description will proceed in the following order.

1. Investigation of medical support arm apparatus

2. First embodiment

-   -   2-1. Configuration of support arm apparatus        -   2-1-1. Overall configuration        -   2-1-2. Configuration of actuator    -   2-2. System configuration of support arm apparatus    -   2-3. Control method        -   2-3-1. Brake release control        -   2-3-2. Brake engagement control    -   2-4. Functional configuration of motor controller

3. Second embodiment

-   -   3-1. Control method        -   3-1-1. Brake release control        -   3-1-2. Brake engagement control    -   3-2. Functional configuration of motor controller

4. Modifications

5. Experiment results

6. Supplement

1. Investigation of Medical Support Arm Apparatus

A medical support arm apparatus supports an observation unit or atreatment tool on the front end of an arm section, and is used toprovide assistance with medical procedures such as surgeries andexaminations performed by a surgeon. For example, with a medical supportarm apparatus, there are anticipated uses such as enlarged observationof a tiny region of an operative site by an observation unit such as animaging unit (also called an electronic imaging microscope), andgrasping a patient's organ or the like by a treatment tool such asforceps.

Herein, in some medical support arm apparatus, a motor and a brake areprovided in each joint section, and the operation of the arm section iscontrolled by the motor and the brake. For example, in a case of wantingto move an observation unit or a treatment tool to a desired position,and locking the observation unit or the treatment tool at the position,the brake is engaged while a supply of current to the motor is alsostopped, and the position and the attitude of the arm section arelocked. In the following description, such a state in which each jointsection is locked by the brake (that is, a state in which the positionand the attitude of the arm section are locked) is also called thelocked state.

In the locked state, in a case in which a need to change the position ofthe observation unit or treatment tool is produced, the brake isreleased while current is also supplied to the motor, the motor isdriven in accordance with regular control (for example, position controlor force control), and the arm section operates in accordance with theregular control. In the following description, such a state in which thedriving of each joint section is controlled in accordance with apredetermined control method during regular operation (that is, a statein which the position and the attitude of the arm section are able tooperate in accordance with a predetermined control method during regularoperation) is also called the regular operating state.

Herein, particularly in a medical support arm apparatus, the movementamount of the arm section when switching between the locked state andthe regular operating state is demanded to be extremely small. This isbecause if the arm section moves, and the position of the observationunit or the treatment tool changes, it becomes necessary to correct theposition of the observation unit or the treatment tool, thereby impedingthe smooth execution of a medical procedure. Particularly, in a case ofperforming enlarged observation of a tiny site with an observation unit,even slight movements of the observation unit cause the field of view tochange greatly, and thus it is desirable to keep the movement amount ofthe observation unit as small as possible.

Also, a medical support arm apparatus is demanded to be compact, so asnot to be an obstacle to the surgeon. For example, with a medicalsupport arm apparatus, there is anticipated a usage scenario in which animage of an operative site taken by the observation unit is projectedonto a display apparatus inside the operating room, and the surgeonperforms surgery while watching the image. In this case, if theconfiguration of the arm section is large, there is a risk that thefield of view of the surgeon watching the display apparatus may beblocked, or that the arm section may hinder the surgeon's work on theoperative site.

To configure the arm section more compactly, further miniaturization ofthe motor provided in each joint section is also demanded. Consequently,since the motor needs to have a predetermined driving force while alsobeing compact, there is a tendency to generate more heat as compared toa large-sized motor. Thus, to inhibit the generation of heat, proactiveutilization of the brake when stationary is anticipated. In this way, ina medical support arm apparatus, a high frequency of switching betweenthe locked state and the regular operating state is anticipated, andthus keeping the movement amount of the arm section small when switchingis more important.

Accordingly, the inventors thoroughly investigated technology capable offurther suppression of the movement of the arm section when switchingbetween the locked state and the regular operating state. The followingdescribes a preferred embodiment of the present disclosure conceived bythe inventors as a result of the investigation. Note that, in light ofthe above circumstances, the technology that may be provided in thepresent disclosure can be said to exhibit a large effect particularly ina medical support arm apparatus. Accordingly, as one example, thefollowing will describe an embodiment in which technology according tothe present disclosure is applied to a medical support arm apparatus.However, the present disclosure is not limited to such an example, andthe present disclosure may also target an industrial support armapparatus used for product assembly, product inspection, or the like ina factory, for example.

2. First Embodiment 2-1. Configuration of Support Arm Apparatus 2-1-1.Overall Configuration

An overall configuration of a support arm apparatus according to a firstembodiment of the present disclosure will be described with reference toFIG. 1. FIG. 1 is a diagram illustrating an overall configuration of asupport arm apparatus according to the first embodiment.

Referring to FIG. 1, a support arm apparatus 400 is equipped with a basesection 410, an arm section 420, and a control apparatus 430. Thesupport arm apparatus 400 is a medical support arm apparatus that may beapplied favorably to surgeries, examinations, and the like.

The base section 410 is a base for the support arm apparatus 400, andthe arm section 420 is extended from the base section 410. The basesection 410 is provided with casters, and the support arm apparatus 400is grounded on the floor face via the casters and configured to bemovable on the floor face with the casters. However, the configurationof the support arm apparatus 400 according to the first embodiment isnot limited to such an example. For example, the support arm apparatus400 may be configured in which the base section 410 is not provided, andthe arm section 420 is attached directly to the ceiling or a wall of theoperating room.

For example, in the case in which the arm section 420 is attached to theceiling, the support arm apparatus 400 is configured so that the armsection 420 hangs down from the ceiling.

The arm section 420 includes multiple joint sections 421 a to 421 f,multiple links 422 a to 422 d that are connected with one another by thejoint sections 421 a to 421 e, and an imaging unit 423 installed at thefront end of the arm section 420.

The links 422 a to 422 d are rod-like members. One end of the link 422 ais connected with the base section 410 through the joint section 421 a,the other end of the link 422 a is connected with one end of the link422 b through the joint section 421 b, and the other end of the link 422b is further connected with one end of the link 422 c through the jointsections 421 c and 421 d. Furthermore, the other end of the link 422 cis connected with one end of the approximately L-shaped link 422 dthrough the joint section 421 e, while the other end of the link 422 dand the imaging unit 423 are connected through the 421 f. As describedabove, the arm shape extending from the base section 410 is configuredsuch that the base section 410 serves as a support point, and the endsof the multiple links 422 a to 422 d and the imaging unit 423 areconnected with one another through the joint sections 421 a to 421 f.

The imaging unit 423 is an example of an observation unit for observingan operative site, and is a camera or the like capable of taking amoving image and/or a still image of an imaging target, for example. Animage of the patient's operative site taken by the imaging unit 423 isdisplayed on a display apparatus (not illustrated) provided in theoperating room, for example, and the surgeon performs surgery whileobserving the image of the patient's operative site displayed on thedisplay apparatus. In this way, the support arm apparatus 400 may be theobservation apparatus 400 in which an observation unit is attached tothe front end of the arm section 420. As the observation unit, otherapparatus may be provided, such as an endoscope, or an opticalmicroscope by which the surgeon performs enlarged observation of theoperative site directly through an eyepiece, for example. Note thatamong types of observation apparatus 400, the support arm apparatus 400in which the imaging unit 423 is provided on the front end of the armsection 420 is also called a video microscope apparatus 400.

However, the front end unit provided on the front end of the arm section420 is not limited to an observation unit, and any of various types ofmedical tools may be attached to the front end of the arm section 420 asthe front end unit. For example, any of various types of treatmenttools, such as forceps or a retractor, may be connected as the front endunit. Alternatively, a light source for an endoscope or a microscope, ora surgical energy device used to seal blood vessels, for example, may beconnected as the front end unit.

The joint sections 421 a to 421 f are provided with actuators 300illustrated in FIG. 2 to be described later, and the joint sections 421a to 421 f are configured to be rotatable about predetermined rotatingshafts according to the driving of motors 310 of the actuators 300. Thedriving of the motors 310 is controlled by the control apparatus 430. Bycontrolling the driving of the motor 310 in each of the joint sections421 a to 421 f, driving of the arm section 420 is controlled so as toextend or contract (fold up) the arm section 420, for example.

Also, a brake that restrains the rotating shaft of the joint sections421 a to 421 f is provided in the actuator 300. Additionally, by controlfrom the control apparatus 430, the state of each joint section isswitched between a locked state and a regular operating state. In thefollowing description, a control that switches the locked state to theregular operating state is also called the brake release control, whilea control that switches the regular operating state to the locked stateis also called the brake engagement control. Details about the brakerelease control and the brake engagement control will be described fullyin (2-3. Control method) below.

Note that, in the illustrated example, the support arm apparatus 400includes six joint sections 421 a to 421 f, and six degrees of freedomare realized with respect to the driving of the arm section 420. Byconfiguring the arm section 420 to have six degrees of freedom, theimaging unit 423 can be moved freely within the movable range of the armsection 420. Consequently, it becomes possible to use the imaging unit423 to image the operative site from a variety of angles and distances.However, the configuration of the arm section 420 is not limited to theillustrated example, and the numbers of the joint sections 421 a to 421f and the links 422 a to 422 c, their arrangement, the directions of thedrive shafts of the joint sections 421 a to 421 f, and the like may beset appropriately so that the arm section 420 has the desired degrees offreedom. However, in consideration of freedom in the position and theattitude of the imaging unit 423, the arm section 420 favorably may beconfigured to have six or more degrees of freedom.

The control apparatus 430 includes a processor, such as a centralprocessing unit (CPU) or a digital signal processor (DSP), for example,or a microcontroller, a control board or the like with these processorsinstalled onboard. By executing signal processing according to apredetermined program, the control apparatus 430 controls the operationof the support arm apparatus 400.

The method of controlling the support arm apparatus 400 is notparticularly limited, and the operation of the support arm apparatus 400may be controlled by the control apparatus 430 by any of various knowncontrol methods, such as position control or force control. In the caseof controlling the support arm apparatus 400 by position control, aninput apparatus such as a controller for operating the arm section 420may be provided. In the case of controlling the support arm apparatus400 by force control, the operation of the arm section 420 may becontrolled so that the arm section 420 moves in the direction of theforce applied to the arm section 420 in response to an operationattempting to move the arm section 420 which is performed by a usertouching the arm section 420 directly, for example. Note that, since anyof various known methods may be used as the specific methods ofcontrolling the support arm apparatus 400 by position control or forcecontrol, a detailed description is omitted herein.

In addition, the control apparatus 430 switches the locked state and theregular operating state by appropriately controlling the operation ofthe actuator 300 in the joint sections 421 a to 421 f of the arm section420. Details about the control during switching will be described fullyin (2-2. System configuration of support arm apparatus) below and in(2-3. Control method) below.

Note that, in the illustrated example, the control apparatus 430 isconnected to the base section 410 through a cable, but by providing acontrol board or the like having functions similar to those of thecontrol apparatus 430 internally inside the base section 410, the basesection 410 and the control apparatus 430 may be configured in anintegrated manner. Alternatively, the functions of the control apparatus430 may be distributed among multiple control boards or the like, andthese multiple control boards or the like may be disposed in the basesection 410 and the arm section 420 in a distributed manner. Forexample, a control board (corresponding to a motor controller 200described later) or the like for controlling the driving of the actuator300 in each of the joint sections 421 a to 421 f may be provided neareach of the joint sections 421 a to 421 f.

The above thus describes a schematic configuration of the support armapparatus 400 according to the first embodiment with reference to FIG.1.

2-1-2. Configuration of Actuator

A configuration of the actuator 300 provided in each of the jointsections 421 a to 421 f of the support arm apparatus 400 illustrated inFIG. 1 will be described with reference to FIG. 2. FIG. 2 is an explodedperspective view illustrating an exemplary configuration of the actuator300 provided in each of the joint sections 421 a to 421 f of the supportarm apparatus 400 according to the first embodiment.

Referring to FIG. 2, the actuator 300 is provided with a motor 310, aspeed reducer 320, an input shaft encoder 330, an output shaft encoder340, an output shaft 350, a housing 360, a brake 370, and a torquesensor 380. In the actuator 300, the rotation of the rotating shaft ofthe motor 310 is reduced by the speed reducer 320 at a predeterminedreduction ratio, and transmitted to other downstream members through theoutput shaft 350. As a result, the other members are driven.

The housing 360 has an approximately cylindrical shape, in which therespective component members are housed internally. In a state in whicheach of the component members is housed inside the housing 360, theactuator 300 is installed into each of the joint sections 421 a to 421 fof the support arm apparatus 400 described above.

The motor 310 is a driving mechanism that, in a case of being given apredetermined command value (current value), causes a rotating shaft torotate at torque corresponding to the command value, thereby producingdriving force. As the motor 310, a brushless motor is used, for example.However, the first embodiment is not limited to such an example, and anyof various known types may be used as the motor 310.

The speed reducer 320 is joined to the rotating shaft of the motor 310.The speed reducer 320 reduces the rotational velocity of the rotatingshaft of the joined motor 310 (in other words, the rotational velocityof the input shaft) at a predetermined reduction ratio, and transmits tothe output shaft 350. In the first embodiment, the configuration of thespeed reducer 320 is not limited to a specific configuration, and any ofvarious known types may be used as the speed reducer 320. However, asthe speed reducer 320, it is favorable to use one capable of setting arelatively large reduction ratio, such as a Harmonic Drive (registeredtrademark), for example. In addition, the reduction ratio of the speedreducer 320 may be set appropriately according to the application of theactuator 300. For example, in the case of applying the actuator 300 tothe joint sections 421 a to 421 f of the support arm apparatus 400 as inthe first embodiment, the speed reducer 320 having a reduction ratio ofapproximately 1:100 may be used favorably.

The input shaft encoder 330 detects the rotational angle of the inputshaft (that is, the rotational angle of the motor 310). The output shaftencoder 340 detects the rotational angle of the output shaft 350. Theconfiguration of the input shaft encoder 330 and the output shaftencoder 340 is not limited, and any of various known types of rotaryencoders, such as magnetic encoders or optical encoders, for example,may be used as the input shaft encoder 330 and the output shaft encoder340.

The brake 370 has a function of restraining the rotating shaft of theactuator 300, and stopping the rotation of the actuator 300. In theillustrated example, the brake 370 is configured in an integrated mannerwith the input shaft encoder 330, and is configured to stop the rotationof the actuator 300 by restraining the rotating shaft of the motor 310(that is, the input shaft). Note that the specific configuration of thebrake 370 is not limited, and any of various known types of brakes, suchas an electromagnetic brake, for example, may be used as the brake 370.

Note that in the actuator 300, since the speed reducer 320 is providedbetween the input shaft and the output shaft 350, the torque of theoutput shaft 350 becomes greater relatively. Consequently, in thehypothetical case of providing the brake 370 on the output shaft 350, alarger braking force is required of the brake 370. Thus, there is apossibility that the brake 370 may be bulkier. In the first embodiment,by providing the brake 370 on the input shaft as illustrated in thedrawing, the actuator 300, that is, the joint sections 421 a to 421 f,can be miniaturized further.

The torque sensor 380 measures the torque produced in the output shaft350. The torque sensor 380 is able to detect both the torque (generatedtorque) output by the motor 310, and the torque (external torque)imparted from the outside. In the illustrated example, the torque sensor380 is configured in an integrated manner with the output shaft encoder340. Note that the specific configuration of the torque sensor 380 isnot limited, and any of various known types of force sensors, such as astrain sensor, for example, may be used as the torque sensor 380.

Note that the arrangement of the brake 370 and the torque sensor 380 isnot limited to the illustrated example. The brake 370 may also bearranged as a member different from the input shaft encoder 330.Additionally, the torque sensor 380 may also be arranged as a memberdifferent from the output shaft encoder 340.

The above describes a configuration of the actuator 300 according to thefirst embodiment with reference to FIG. 2. Note that the actuator 300additionally may be provided with other components besides theillustrated components. For example, the actuator 300 additionally maybe provided with any of various types of members that may be included ina typical actuator, such as a driver circuit (driver integrated circuit(IC)) that induces rotational driving in the motor 310 by supplying acurrent to the motor 310.

Herein, as described above, the actuator 300 is an actuator with abuilt-in brake, in which the brake 370 is attached directly to the driveshaft (input shaft) of the motor 310.

Generally, in the control during regular operation, such as positioncontrol or force control, a control quantity necessary to realize adesired position and attitude is computed by sensing the position andthe attitude of the arm section 420 on the basis of measurement valuesof the rotational angle and the torque of the actuator 300 in each ofthe joint sections 421 a to 421 f. On the other hand, as above, in theactuator 300, the rotation of the drive shaft of the motor 310 isstopped directly by the brake 370. Consequently, attempting to conductcontrol during regular operation while still in the locked state resultsin a state in which the measurement value of the input shaft encoder 330or the output shaft encoder 340 does not change even through the motor310 is driving, thus producing a malfunction in the control.

Therefore, with an actuator with a built-in brake like the actuator 300,switching between the locked state and the regular operating staterequires that the control during regular operation be started afterreleasing the brake, so that these two states do not overlap in time.However, in the case of simply conducting such a switching control, anexclusive time occurs in which the brake is not engaged and the controlduring regular operation is also not started, and a situation may occurin which the arm section moves greatly due to its own weight.

Accordingly, in the first embodiment, in the control that switches thelocked state to the regular operating state (hereinafter also called thebrake release control) and in the control that switches the regularoperating state to the locked state (hereinafter also called the brakeengagement control), control is conducted to keep the movement amount ofthe arm section 420 even smaller. Hereinafter, the brake release controland the brake engagement control according to the first embodiment willbe described in detail.

2-2. System Configuration of Support Arm Apparatus

A system configuration of a support arm apparatus according to the firstembodiment will be described with reference to FIG. 3. FIG. 3 is a blockdiagram illustrating a system configuration of a support arm apparatusaccording to the first embodiment. Note that FIG. 3 illustrates thesystem of the support arm apparatus 400 described with reference to FIG.1 in a simulated manner as blocks and connections between the blocks.

Note that, in FIG. 3, to describe the brake release control and thebrake release control according to the first embodiment, only thecomponents necessary for these controls are illustrated primarily, whilethe other components are omitted from illustration. However, the supportarm apparatus 400 may include components for realizing various types ofoperations which are executable by a typical existing support armapparatus, such as components for causing the arm section 420 to operateby position control or force control, for example.

Referring to FIG. 3, the support arm apparatus 400 primarily includes acontrol system 100, the actuator 300 provided in each of the jointsections 421 a to 421 f of the arm section 420, and a motor controller200 which is provided with respect to each actuator 300, and controlsthe operation of each actuator 300. Note that the actuator 300corresponds to the actuator 300 described with reference to FIG. 2.

The motor controller 200, in accordance with control from the controlsystem 100, controls the driving of the motor 310 and the brake 370 ofthe actuator 300 assigned to itself. Specifically, the motor controller200, in accordance with control from the control system 100, executesthe brake release control (that is, releases the brake 370 while alsodriving the motor 310 in accordance with the control during regularoperation). In addition, the motor controller 200, in accordance withcontrol from the control system 100, executes the brake engagementcontrol (that is, engages the brake 370 to lock each of the jointsections 421 a to 421 f while also stopping the supply of current to themotor 310).

Additionally, during regular operation, the motor controller 200, inaccordance with control from the control system 100, controls thedriving of the motor 310 so that each of the joint sections 421 a to 421f rotates by an amount corresponding to a control quantity computed inaccordance with a predetermined method of position control or forcecontrol. Note that since any of various known methods may be used as thespecific methods of position control or force control, a detaileddescription is omitted herein.

Note that, as an actual apparatus configuration, the multiple motorcontrollers 200 may be different configurations, or the functionsthereof may be aggregated all together in a single configuration (suchas a control board or the like, for example). For example, a controlboard or the like having functions corresponding to the single motorcontroller 200 may be provided in each of the joint sections 421 a to421 f, or the functions of the multiple motor controllers 200 may beaggregated inside the control apparatus 430 illustrated in FIG. 1.

The control system 100 centrally controls the operation of the armsection 420 by controlling the operations of the multiple motorcontrollers 200 in a coordinated manner. Specifically, the controlsystem 100, by appropriately controlling the operations of each motorcontroller 200, causes each motor controller 200 to execute the brakerelease control and the brake engagement control. Also, during regularoperation, the control system 100 computes a control quantity withrespect to the motor 310 in each of the joint sections 421 a to 421 f inaccordance with any of various known types of methods of positioncontrol or force control, and causes each motor controller 200 to drivethe motor 310 in accordance with the control quantity. Note that thefunctions of the control system 100 may be realized by the controlapparatus 430 illustrated in FIG. 1, for example.

The operations of the arm section 420 in accordance with the brakerelease control, the brake engagement control, and the control duringregular operation in the control system 100 may be conducted inaccordance with operation input by a user through a user interface 110.Operation input by the user may be conducted through an input devicesuch as a lever or switch, for example, or may be conducted by a directoperation with respect to the arm section 420, like moving the armsection 420 directly by hand. Specifically, for example, the switchingof these controls may be conducted explicitly by an operation withrespect to a switch or the like. Alternatively, for example, the controlsystem 100 may execute the brake release control in the case in whichthe user attempts to move the arm section 420 directly by hand, and thecontrol system 100 may execute the brake engagement control in the casein which the user removes one's hand from the arm section 420.

2-3. Control Method

Details about the brake release control and the brake engagement controlaccording to the first embodiment executed in the system configurationillustrated in FIG. 3 will be described. Note that each of the processesillustrated in FIGS. 4 and 5 described below corresponds to a processexecuted with respect to each corresponding actuator in each of themotor controllers 200 illustrated in FIG. 3.

2-3-1. Brake Release Control

A processing procedure of the brake release control according to thefirst embodiment will be described with reference to FIG. 4. FIG. 4 is aflowchart illustrating an example of a processing procedure of the brakerelease control according to the first embodiment.

Referring to FIG. 4, in the brake release control according to the firstembodiment, first, a command to conduct the control during regularoperation in the actuator 300, or in other words, a command to releasethe brake 370, is input (step S101). In the case in which the positionand the attitude of the arm section 420 are locked by the brake 370, thecommand may be issued from the control system 100 to each motorcontroller 200 in response to an operation of the user attempting tomove the arm section 420.

Next, a measurement value of the torque sensor 380 is acquired, and acurrent value for driving the motor 310 is computed on the basis of themeasurement value (step S103). Specifically, in step S103, first, in thestate in which the position and the attitude of the arm section 420 arelocked by the brake 370, the measurement value of the torque sensor 380is used to compute a necessary torque value that the motor 310 shouldoutput for the state to be realized by the motor 310 of the actuator 300(that is, a torque value that the motor 310 should output so that, evenin the case in which the brake 370 is released, the position and theattitude of the arm section 420 may still be maintained by the motor310). Subsequently, a current value necessary to output the computedtorque value is computed from a torque constant of the motor 310.

Subsequently, the motor 310 is driven in accordance with the computedcurrent value (step S105). Hereinafter, such a control of driving themotor 310 by a current value tracking a measurement value of a torquesensor so that the position and the attitude of the arm section 420 aremaintained will be called the current tracking control for the sake ofconvenience, in order to distinguish from the regular position controlor force control.

After the current tracking control is conducted, next, the release ofthe brake 370 is started (step S107). In this way, in the firstembodiment, the release of the brake 370 is started in a state in whichthe current tracking control is being executed.

Next, it is determined whether or not a fixed time has elapsed (stepS109). Only in the case in which the fixed time has elapsed, the flowproceeds to step S111, and the switching from the current trackingcontrol to the control during regular operation (that is, positioncontrol or force control) is conducted. In other words, the switchingfrom the current tracking control to the control during regularoperation is conducted after standing by until a fixed time elapses fromthe start of the release of the brake 370.

The fixed time may be a time from the start of the release of the brake370 until the brake 370 is actually released. In other words, theprocess in step S109 is a process of standing by until the release ofthe brake 370 functions effectively. This is because generally, in thebrake 370, during the period from the start of release until themechanical mechanism that is restraining the rotating shaft actuallyreleases the restraint completely, a predetermined time lag is produced,such as the time during which the mechanism moves physically. The timeis defined as a specification in accordance with the type of the brake370, for example. Consequently, the specific value of the fixed time instep S109 may be set appropriately in accordance with the specificationsof the brake 370. For example, the fixed time may be approximately fromseveral dozen to several hundred milliseconds.

The above describes a processing procedure of the brake release controlaccording to the first embodiment with reference to FIG. 4. As describedabove, according to the first embodiment, when transitioning from thelocked state to the regular operating state, the brake 370 is releasedafter the current tracking control is conducted. Herein, in the currenttracking control, the load acting on each actuator 300 after the releaseof the brake 370 is predicted on the basis of the measurement value ofthe torque sensor 380, and the motor 310 is driven by a current value bywhich a torque corresponding to the load is output. Consequently,according to the first embodiment, in the instant when the brake 370 isreleased, even though the control during regular operation is not beingconducted yet, the position and the attitude of the arm section 420 maybe maintained by the current tracking control, and thus the movementamount of the imaging unit 423 is suppressed further. Thus, smoothexecution of medical procedures is realized, without the surgeon's workbeing impeded.

Herein, as another method of control when transitioning from the lockedstate to the regular operating state, a method of beginning to start thecontrol during regular operation in a dead time from beginning torelease the brake until the brake is actually released is conceivable.However, with this method, to ensure a margin while accounting forvariations, an exclusive time occurs in which the brake is not engagedand the control during regular operation is also not functioningnormally, and there is a risk of the position and the attitude of thearm section changing greatly. According to the first embodiment, bybeginning to release the brake 370 after conducting the current trackingcontrol as above, the occurrence of such an exclusive time can beprevented.

Also, in the first embodiment, the current tracking control may beconducted dynamically on the basis of the measurement value of thetorque sensor. Herein, with existing technology as exemplified by PatentLiterature 1, a compensation amount of the change in the position andthe attitude of the arm section is computed on the basis of a parameterwhich is a fixed value. However, due to differences in the attitude ofthe arm section 420 and the external environment, such as the ambienttemperature, the torque acting on each joint section (actuator 300) isdifferent. Consequently, with such existing technology, there is apossibility of being unable to effectively suppress changes in theposition and the attitude of the arm section. On the other hand, in thefirst embodiment, since the current tracking control is conducteddynamically on the basis of the measurement value of the torque sensoras above, the torque that the motor 310 should output at the time iscomputed dynamically in accordance with the attitude of the arm section420 and the external environment, and changes in the position and theattitude of the arm section 420 can be suppressed with higher accuracy.

Also, generally, in the case of controlling a certain physical quantityto match a predetermined target value, in the case of a large differencebetween the target value and the current value, the overshoot in theresponse and the time until convergence become greater (that is, thetransient response worsens). For example, like the example describedabove, in the case in which the control during regular operation isstarted after releasing the brake, the generated torque of the motorwhen the control during regular operation is started is approximatelyzero, and from this state the motor must be controlled so that thegenerated torque tracks a predetermined target value. Thus, thetransient response is thought to worsen readily.

On the other hand, in the first embodiment, when the control duringregular operation is started, the current tracking control is alreadybeing conducted. Also, since the current tracking control is beingconducted to maintain the position and the attitude of the arm section420 when the control during regular operation is started, when thecurrent tracking control is switched to the control during regularoperation, a value close to the target value of the generated torquewhen the control during regular operation is started (that is, a targetvalue of the current to apply to the motor 310) is already realized.Consequently, when the control during regular operation is started, thetarget value does not fluctuate greatly, and worsening of the transientresponse is restrained. Thus, changes in the position and the attitudeof the arm section 420 attendant on the switching of states may besuppressed further.

Note that, in the first embodiment, the respective torque constants ofeach motor 310 provided in each actuator 300 may be stored in a storagearea in each actuator 300, a storage area in each motor controller 200,or the like. In addition, in the current tracking control, a targetvalue of current may be computed for each actuator 300 by using thetorque constant corresponding to the motor 310 provided in the actuator300 itself. Generally, since the torque constant is a unique constantthat varies for each motor 310, by using a torque constant correspondingto each motor 310 in this way, the current tracking control can beconducted with higher accuracy. Additionally, the torque constant mayalso change due to temperature. Consequently, in the first embodiment, atemperature sensor may be provided in the actuator 300, and the currenttracking control may also be conducted after correcting the torqueconstant on the basis of a measurement value of the temperature sensor.Furthermore, it is known that the torque constant may also vary due tothe angle of the rotating shaft of the motor 310, the magnitude of thecurrent applied to the motor 310, and the like. Consequently, thecurrent tracking control may also be conducted after correcting thetorque constant on the basis of the angle of the rotating shaft detectedby the input shaft encoder 330 or the output shaft encoder 340, or thecurrent value currently being applied to the motor 310. By conductingthese correction processes, the accuracy of the current tracking controlcan be improved further.

Note that, as described above, the process in step S109 is a process ofstanding by until the release of the brake 370 functions effectively. Inthe example illustrated in FIG. 4, the process is a process of standingby until a fixed time elapses, but the first embodiment is not limitedto such an example. In step S109, a process that confirms whether or notthe release of the brake 370 is functioning effectively may also beconducted. Subsequently, as a result of the process, in the case ofdetermining that the release of the brake 370 is functioningeffectively, the switching from the current tracking control to thecontrol during regular operation may be conducted.

For example, in step S109, on the basis of a measurement value of theoutput shaft encoder 340, in the case in which the angle of the outputshaft changes a predetermined value or more, it may be determined thatthe release of the brake 370 is functioning effectively. This is becauseeven in the case in which the current tracking control is beingconducted, when the brake 370 is released, the rotational angle of theoutput shaft is thought to change, even if only slightly (see FIG. 12described later).

Herein, in the first embodiment, by using a measurement value of theoutput shaft encoder 340 rather than a measurement value of the inputshaft encoder 330, the release of the brake 370 can be determined withhigher accuracy. The reason for this is because, as described withreference to FIG. 2, in the actuator 300 according to the firstembodiment, the speed reducer 320 and the torque sensor 380 are providedbetween the motor 310 and the output shaft 350, and thus backlash of thespeed reducer 320, strain of the torque sensor 380, and the like maycause a discrepancy to occur in the transmission of the angle betweenthe motor shaft and the output shaft 350. In other words, there is apossibility that the measurement value of the input shaft encoder 330does not necessarily indicate the rotational angle of the output shaft350 accurately. Consequently, by using a measurement value of the outputshaft encoder 340, the angle change of the output shaft 350 can beascertained with higher accuracy, and the determination of whether ornot the brake 370 has been released according to the angle change can beconducted with higher accuracy.

2-3-2. Brake Engagement Control

A processing procedure of the brake engagement control according to thefirst embodiment will be described with reference to FIG. 5. FIG. 5 is aflowchart illustrating an example of a processing procedure of the brakeengagement control according to the first embodiment.

Referring to FIG. 5, in the brake engagement control according to thefirst embodiment, first, a brake locking command, that is, a command tostop the control during regular operation in the actuator 300 and lockthe joint section with the brake 370, is input (step S201). The commandmay be issued from the control system 100 to each motor controller 200in response to an operation of the user attempting to engage the brake370.

Next, a measurement value of the torque sensor 380 is acquired, and acurrent value for driving the motor 310 is computed on the basis of themeasurement value (step S203). Specifically, in step S203, a currentvalue for conducting the current tracking control is computed, similarlyto the process in step S103 in the brake release control describedabove. In other words, the measurement value of the torque sensor 380 isused to compute a necessary torque value that the motor 310 shouldoutput for the current state of attempting to lock the position and theattitude of the arm section 420 with the brake 370 to be realized by themotor 310 of the actuator 300 (that is, a torque value that the motor310 should output so that, even in the state in which the brake 370 isnot engaged, the position and the attitude of the arm section 420 maystill be maintained by the motor 310). Subsequently, a current valuenecessary to output the computed torque value is computed from a torqueconstant of the motor 310.

Subsequently, the motor 310 is driven in accordance with the computedcurrent value, that is, the switching from the control during regularoperation to the current tracking control is conducted (step S205).

After the current tracking control is conducted, next, the locking ofthe rotating shaft by the brake 370 is started (step S207). In this way,in the first embodiment, the locking by the brake 370 is started in astate in which the current tracking control is being executed.

Next, it is determined whether or not a fixed time has elapsed (stepS209). Only in the case in which the fixed time has elapsed, the flowproceeds to step S211, and the current tracking control is stopped. Inother words, the current tracking control is stopped after standing byuntil a fixed time elapses from the start of the locking of the rotatingshaft by the brake 370.

The fixed time may be a time from the start of the locking of therotating shaft by the brake 370 until the locking of the rotating shaftby the brake 370 actually functions. In other words, the process in stepS209 is a process of standing by until the locking by the brake 370functions effectively. This is because, similar to when releasing thebrake, generally, in the brake 370, during the period from the start ofthe locking of the rotating shaft until the mechanical mechanism forrestraining the rotating shaft actually completes the restraintentirely, a predetermined time lag occurs, such as the time during whichthe mechanism moves physically. The time is defined as a specificationin accordance with the type of the brake 370, for example. Consequently,the specific value of the fixed time in step S209 may be setappropriately in accordance with the specifications of the brake 370.For example, the fixed time may be approximately from several dozen toseveral hundred milliseconds.

The above describes a processing procedure of the brake engagementcontrol according to the first embodiment with reference to FIG. 5.According to the brake engagement control according to the firstembodiment, effects similar to those of the brake release controldescribed above can be obtained. Namely, according to the brakeengagement control according to the first embodiment, when transitioningfrom the regular operating state to the locked state, the rotating shaftis locked by the brake 370 after switching from the control duringregular operation to the current tracking control. Consequently, in theinstant when the rotating shaft is locked by the brake 370, even thoughthe control during regular operation is not being conducted, theposition and the attitude of the arm section 420 are maintained by thecurrent tracking control, and thus the movement amount of the imagingunit 423 is suppressed further. Thus, smooth execution of medicalprocedures is realized, without the surgeon's work being impeded. Also,at this time, since the current tracking control is conducteddynamically on the basis of a measurement value of a torque sensor,dynamic current tracking control corresponding to changes in theattitude of the arm section 420 and changes in the external environmentcan be conducted, and changes in the position and the attitude of thearm section 420 can be suppressed further.

Note that, in the brake engagement control, similarly to the brakerelease control, the current tracking control may be conducted using aunique torque constant for each motor 310. At this time, a temperaturecorrection with respect to the torque constant may also be conducted inaddition.

Additionally, the process in step S209 may be another process insofar asthe process is capable of determining that the locking of the rotatingshaft by the brake 370 is functioning effectively. At this time, byusing a measurement value of the output shaft encoder 340 for thedetermination, a more accurate determination process, from which theinfluence of backlash of the speed reducer 320, strain of the torquesensor 380, and the like has been eliminated, can be conducted.

2-4. Functional Configuration of Motor Controller

A functional configuration of the motor controller 200 for executing thebrake release control and the brake engagement control according to thefirst embodiment described above will be described with reference toFIG. 6. FIG. 6 is a block diagram illustrating an example of afunctional configuration of the motor controller 200 according to thefirst embodiment. Note that, in FIG. 6, the actuator 300 is alsoillustrated in addition for the sake of explanation.

Referring to FIG. 6, the motor controller 200 is provided with a currentvalue computation section 201, a motor control section 203, and a brakecontrol section 205 as functions thereof. These functions may berealized by having a processor included in the motor controller 200conduct computational processing following a predetermined program.

The motor control section 203 controls the driving of the motor 310 ofthe actuator 300. The brake control section 205 controls the driving ofthe brake 370 of the actuator 300.

The current value computation section 201 acquires a measurement valuefrom the torque sensor 380 of the actuator 300, and, on the basis of themeasurement value, computes a current value to be given to the motor 310in the current tracking control. In other words, on the basis of ameasurement value of the torque sensor 380, the current valuecomputation section 201 computes a torque value that the motor 310 ofthe actuator 300 should output to maintain the current position andattitude of the arm section 420, and uses a torque constant to compute acurrent value to be supplied to the motor 310 to output the torquevalue.

During the brake release control, the series of processes illustrated inFIG. 4 described above is executed by the current value computationsection 201, the motor control section 203, and the brake controlsection 205. Namely, when a command to release the brake 370 and drivethe actuator 300 in accordance with the control during regular operationis input (corresponding to the process in step S101), a measurementvalue of the torque sensor 380 is acquired and a current value for thecurrent tracking control is computed by the current value computationsection 201 (corresponding to the process in step S103).

Subsequently, on the basis of the current value computed by the currentvalue computation section 201, the motor control section 203 drives themotor 310, thereby causing the current tracking control to be conducted(corresponding to the process in step S105). Information indicating thatthe current tracking control has been started is provided from the motorcontrol section 203 to the brake control section 205, and the brakecontrol section 205 starts the release of the brake 370 (correspondingto the process in step S107).

Subsequently, after the fixed time elapses (corresponding to the processin step S109), the motor control section 203 switches the control of themotor 310 from the current tracking control to the control duringregular operation (corresponding to the process in step S111). Duringregular operation, the motor control section 203 drives the motor 310 inaccordance with a control quantity required in accordance with a methodof position control or force control in the control system 100illustrated in FIG. 3.

Also, during the brake engagement control, the series of processesillustrated in FIG. 5 described above is executed by the current valuecomputation section 201, the motor control section 203, and the brakecontrol section 205. Namely, when a command to stop the control duringregular operation in the actuator 300 and lock the joint section withthe brake 370 is input (corresponding to the process in step S201), ameasurement value of the torque sensor 380 is acquired and a currentvalue for the current tracking control is computed by the current valuecomputation section 201 (corresponding to the process in step S203).

Subsequently, on the basis of the current value computed by the currentvalue computation section 201, the motor control section 203 drives themotor 310, thereby causing the current tracking control to be conducted(corresponding to the process in step S205). Information indicating thatthe current tracking control has been started is provided from the motorcontrol section 203 to the brake control section 205, and the brakecontrol section 205 starts the locking of the rotating shaft by thebrake 370 (corresponding to the process in step S107).

Subsequently, after the fixed time elapses (corresponding to the processin step S209), the motor control section 203 stops the supply of currentto the motor 310 (that is, stops the current tracking control)(corresponding to the process in step S211).

The above thus describes a functional configuration of the motorcontroller 200 with reference to FIG. 6.

3. Second Embodiment

A second embodiment of the present disclosure will be described. In thesecond embodiment, in addition to the brake release control and thebrake engagement control, a process of detecting an abnormality of themotor 310 or the brake 370 is conducted.

Note that the second embodiment is similar to the first embodimentdescribed above, except that a process of detecting an abnormality isconducted, and the functional configuration of the motor controller 200is changed in association with the addition of the process. Namely, theapparatus configuration of the support arm apparatus 400, theconfiguration of the actuator 300, and the system configuration of thesupport arm apparatus 400 are similar to those in FIGS. 1 to 4. However,in the second embodiment, in the system configuration of the support armapparatus 400 illustrated in FIG. 3, instead of the motor controller200, a motor controller 200 a that includes a function for executingvarious processes according to the second embodiment is provided.Consequently, in the following description of the second embodiment, thefeatures that differ from those of the first embodiment will bedescribed primarily, whereas detailed description of the features thatoverlap with those of the first embodiment will be omitted.

3-1. Control Method

A control method according to the second embodiment executed in thesystem configuration illustrated in FIG. 3 will be described. Note thateach of the processes illustrated in FIGS. 7 and 8 described belowcorresponds to a process executed with respect to each correspondingactuator in each of the motor controllers 200 a.

3-1-1. Brake Release Control

A processing procedure of the brake release control according to thesecond embodiment will be described with reference to FIG. 7. FIG. 7 isa flowchart illustrating an example of a processing procedure of thebrake release control according to the second embodiment.

Note that the processing procedure of the brake release controlaccording to the second embodiment is similar to the brake releasecontrol according to the first embodiment, up to the process in whichthe release of the brake 370 is started. In other words, the processesfrom step S301 to step S307 illustrated in FIG. 7 are similar to theprocesses from step S101 to step S107 illustrated in FIG. 4.Consequently, a description of each of these processes is omittedherein.

In the brake release control according to the second embodiment, whenthe release of the brake is started in step S307, next, it is determinedwhether or not a measurement value of the output shaft encoder 340 haschanged by a predetermined value or more after the fixed time elapses(step S309). Herein, standing by until the fixed time elapses in stepS309 is for standing by until the release of the brake 370 functionseffectively, similar to the process in step S109 illustrated in FIG. 4.In other words, in the second embodiment, in the state in which therelease of the brake 370 is thought to have functioned effectively, itis determined whether or not the measurement value of the output shaftencoder 340 has changed by the predetermined value or more.

At the stage illustrated in step S309, since the current trackingcontrol is being conducted, even if the brake 370 is released, theposition and the attitude of the arm section 420 should still bemaintained mostly as-is. Consequently, in the case in which themeasurement value of the output shaft encoder 340 has not changed by thepredetermined value or more in step S309, it is thought that the currenttracking control is being conducted normally, that is, the motor 310 isoperating normally. Thus, in this case, similarly to the firstembodiment, the switching from the current tracking control to thecontrol during regular operation is conducted (step S311).

On the other hand, in the case in which the measurement value of theoutput shaft encoder 340 has changed by the predetermined value or morein step S309, it is thought that the current tracking control is notbeing conducted normally, that is, the motor 310 is not operatingnormally. Consequently, in this case, control does not transition to thecontrol during regular operation, and the flow proceeds to step S313.

In step S313, the rotating shaft is locked by the brake 370, and thecontrol of the motor 310 is stopped. If the current tracking control iscontinued even though an abnormality has occurred in the motor 310, theposition and the attitude of the arm section 420 cannot be maintained.For this reason, by stopping the current tracking control and engagingthe brake 370, the position and the attitude of the arm section 420 arelocked safely.

Additionally, the user is warned about the abnormality of the motor 310(step S315). The warning may be a visual warning that displays text orthe like on a display apparatus that displays the image taken by theimaging unit 423, and may also be an auditory warning by a buzzer,alarm, or the like, for example.

The above describes a processing procedure of the brake release controlaccording to the second embodiment with reference to FIG. 7.

3-1-2. Brake Engagement Control

A processing procedure of the brake engagement control according to thesecond embodiment will be described with reference to FIG. 8. FIG. 8 isa flowchart illustrating an example of a processing procedure of thebrake engagement control according to the second embodiment.

Note that the brake engagement control according to the secondembodiment is similar to the brake engagement control according to thefirst embodiment, up to the process in which the joint section is lockedby the brake 370 and the current tracking control is stopped. In otherwords, the processes from step S401 to step S411 illustrated in FIG. 8are similar to the processes from step S201 to step S211 illustrated inFIG. 5. Consequently, a description of each of these processes isomitted herein.

In the brake engagement control according to the second embodiment, whenthe current tracking control is stopped in step S411, next, it isdetermined whether or not the measurement value of the output shaftencoder 340 has changed by a predetermined value or more (step S413). Atthe stage illustrated in step S413, the position and the attitude of thearm section 420 should be locked by the functioning of the brake 370.Consequently, in the case in which the measurement value of the outputshaft encoder 340 has not changed by the predetermined value or more instep S413, it is thought that the brake 370 is engaging normally, and nospecial process is conducted.

On the other hand, in the case in which the measurement value of theoutput shaft encoder 340 has changed by the predetermined value or morein step S413, it is thought that the brake 370 is not engaging normally.Consequently, in this case, the flow proceeds to step S415, the brake370 is released, and the control during regular operation is resumed. Inthis case, since the brake 370 is in a state of being unable to lock theposition and the attitude of the arm section 420, by transitioning tothe control during regular operation, the position and the attitude ofthe arm section 420 are maintained safely by the driving force of themotor 310.

Additionally, the user is warned about the abnormality of the brake 370(step S417). The warning may be a visual warning that displays text orthe like on a display apparatus that displays the image taken by theimaging unit 423, and may also be an auditory warning by a buzzer,alarm, or the like, for example.

The above describes a processing procedure of the brake engagementcontrol according to the second embodiment with reference to FIG. 8.

As described above, according to the second embodiment, in the middle ofthe brake release control and the brake engagement control, anabnormality of the motor 310 or the brake 370 is detected on the basisof the measurement value of the output shaft encoder 340. Specifically,in the case in which the measurement value of the output shaft encoder340 changes greatly while releasing the brake 370, an abnormality of themotor 310 is detected, and the position and the attitude of the armsection 420 are locked safely by the brake 370. Also, in the case inwhich the measurement value of the output shaft encoder 340 changesgreatly while locking the rotating shaft with the brake 370, anabnormality of the brake 370 is detected, and the position and theattitude of the arm section 420 are locked safely by the driving forceof the motor 310.

In this way, according to the second embodiment, in addition to theeffects obtained in the first embodiment, there is exhibited a furthereffect by which a safer support arm apparatus 400 may be provided.

Also, this is because, as described above, in the actuator 300, due tobacklash of the speed reducer 320, strain of the torque sensor 380, andthe like, there is a possibility that the measurement value of the inputshaft encoder 330 does not necessarily indicate the rotational angle ofthe output shaft 350 accurately. Consequently, in the second embodiment,like in the examples illustrated in FIGS. 7 and 8, by detecting anabnormality of the motor 310 or the brake 370 using a measurement valueof the output shaft encoder 340 rather than a measurement value of theinput shaft encoder 330, the abnormality can be detected with higheraccuracy.

3-2. Functional Configuration of Motor Controller

A functional configuration of the motor controller 200 a for executingthe brake release control and the brake engagement control according tothe second embodiment described above will be described with referenceto FIG. 9. FIG. 9 is a block diagram illustrating an example of afunctional configuration of the motor controller 200 a according to thesecond embodiment. Note that, in FIG. 9, the actuator 300 is alsoillustrated in addition for the sake of explanation.

Referring to FIG. 9, the motor controller 200 a is provided with acurrent value computation section 201, a motor control section 203, abrake control section 205, and an abnormality detection section 207 asfunctions thereof. These functions may be realized by having a processorincluded in the motor controller 200 a conduct computational processingfollowing a predetermined program. Note that the functions of thecurrent value computation section 201, the motor control section 203,and the brake control section 205 are substantially similar to thesefunctions in the motor controller 200 according to the first embodimentdescribed with reference to FIG. 6, and thus a detailed description willbe omitted herein.

The abnormality detection section 207 acquires a measurement value fromthe output shaft encoder 340 of the actuator 300, and on the basis ofthe measurement value, detects an abnormality of the motor 310 or thebrake 370.

Specifically, in the case in which the measurement value of the outputshaft encoder 340 changes greatly while releasing the brake 370, theabnormality detection section 207 determines that an abnormality isoccurring in the motor 310, and, through the motor control section 203and the brake control section 205, engages the brake 370 while alsostopping the control of the motor 310 (corresponding to the process instep S313). Furthermore, the abnormality detection section 207 issues awarning indicating that an abnormality of the motor 310 has beendetected (corresponding to the process in step S313).

Also, in the case in which the measurement value of the output shaftencoder 340 changes greatly while locking the rotating shaft with thebrake 370, the abnormality detection section 207 determines that anabnormality is occurring in the brake 370, and, through the motorcontrol section 203 and the brake control section 205, releases thebrake 370 while also starting the control of the motor 310(corresponding to the process in step S415). Furthermore, theabnormality detection section 207 issues a warning indicating that anabnormality of the brake 370 has been detected (corresponding to theprocess in step S417).

The above describes a functional configuration of the motor controller200 a with reference to FIG. 9.

4. Modifications

The brake release control and the brake engagement control according tothe first and second embodiments described above are conducted for eachactuator 300 by the motor controller 200 or 200 a provided in eachactuator 300. For example, in the first and second embodiments, thebrake release control or the brake engagement control may be conductedat the same time in each actuator 300.

However, by appropriately controlling the timings at which thesecontrols are conducted in each actuator 300, the amount of change in theposition and the attitude of the arm section 420 can be suppressedfurther. Herein, as a modification of the present embodiment, such anembodiment in which the brake release control or the brake engagementcontrol is conducted at a different timing in each actuator 300 will bedescribed.

FIGS. 10 and 11 are sequence diagrams illustrating an example of aprocessing procedure for a modification in which the brake releasecontrol or the brake engagement control in each actuator 300 isconducted at a different timing. Note that, in FIGS. 10 and 11, sequencediagrams for the case of conducting the brake release control accordingto the first embodiment in each actuator 300 are illustrated as oneexample, but the processing procedure may also be similar for the casein which another control is conducted.

Referring to FIGS. 10 and 11, in the present modification, when anoperator performs a brake release operation, information indicating thatthe brake release operation has been performed is input into the controlsystem 100 (step S501). Subsequently, the control system 100 does nottransmit a brake release command to all of the motor controllers 200 atthe same time, but instead transmits the brake release command to acertain one (in the illustrated example, Motor Controller 1) of themotor controllers 200 (step S503).

The motor controller 200 receiving the brake release command executesthe series of processes (that is, the brake release control) illustratedin FIG. 4 on the actuator 300 corresponding to itself, thereby switchingits state from the locked state to the regular operating state (stepS505).

When the state of the actuator 300 is switched to the regular operatingstate by the brake release control, the motor controller 200 transmits anotification indicating that the brake release control has completed tothe control system 100 (step S507).

The control system 100 receiving the notification transmits the brakerelease command to another (in the illustrated example, Motor Controller2) of the motor controllers 200 (step S509). The motor controller 200receiving the brake release command similarly executes the series ofprocesses (that is, the brake release control) illustrated in FIG. 4 onthe actuator 300 corresponding to itself, thereby switching its statefrom the locked state to the regular operating state (step S511).Subsequently, when the state of the actuator 300 is switched to theregular operating state, the motor controller 200 transmits anotification indicating that the brake release control has completed tothe control system 100 (step S513).

Similarly thereafter, the brake release control is conductedsuccessively on the N actuators 300 included in the support armapparatus 400 (step S515 to step S519).

In the above example, the case of conducting the brake release controlis described, but the same applies to the case of conducting the brakeengagement control. In this way, in the present modification, the brakerelease control or the brake engagement control is conducted at adifferent timing on each actuator 300 included in the support armapparatus 400.

Herein, in the support arm apparatus 400, the position of the front endof the arm section 420 is decided by the attitude of all of the jointsections. Consequently, in the case in which the brake release controlor the brake engagement control is conducted at the same time in all ofthe joint sections, the amounts of change of each of the joint sectionsbecome accumulated more going towards the front end, and the amount ofchange of the position becomes greater. Also, in the case in whichshaking is produced by sympathetic vibration or the like when releasingthe brake 370 or starting the control of the motor 310, in the torquesensors 380 and the output shaft encoders 340 of the other jointsections, the shaking is detected as noise, and there is a risk ofinfluencing the control of the arm section 420.

Accordingly, in the present modification, the brake release control orthe brake engagement control in each actuator 300 is executed at anappropriate timing so that the shaking or the like produced by the brakerelease control or the brake engagement control in each actuator 300 ofeach joint section influences the other joint sections as little aspossible. With this arrangement, changes in the position and theattitude of the front end (that is, the imaging unit 423) of the armsection 420 can be kept to a minimum.

For example, the timing of executing the brake release control or thebrake engagement control may be set appropriately with consideration forhow easily shaking is produced in the arm section 420 when executing thebrake release control or the brake engagement control. How easilyshaking is produced in each joint section may be predicted from theconfiguration of the arm section 420 (such as the arrangement of thejoint sections, the length of each link, and the inertia of each jointsection). For example, shaking produced in a relatively long link whenconducting the brake release control or the brake engagement control ina joint section connected to the link is thought to be greater ascompared to the case in which the link is short. Consequently, thetiming of executing the brake release control or the brake engagementcontrol in each actuator 300 may be set on the basis of theconfiguration of the arm section 420.

Also, how easily shaking is produced in the arm section 420 is alsothought to change depending on the attitude of the arm section 420 whenattempting to conduct the brake release control or the brake engagementcontrol. Consequently, the control system 100 may also detect theattitude of the arm section 420 on the basis of the measurement value ofthe output shaft encoder 340 and the measurement value of the torquesensor 380 of each actuator 300, and, on the basis of the detectedattitude, decide the timing at which to execute the brake releasecontrol or the brake engagement control in each actuator 300.

As an example, to further reduce changes in the position and theattitude of the front end (that is, the imaging unit 423) of the armsection 420, the brake release control or the brake engagement controlmay be executed favorably in order from the joint section (actuator 300)on the front end side of the arm section 420. This is because, althoughshaking produced in a joint section closer to the base end side disposedat a position farther away from the front end is thought to have agreater influence on the front end, if the brake release control or thebrake engagement control in a joint section close to the front end hasalready finished when the brake release control or the brake engagementcontrol is conducted in a joint section on the base end side, theinfluence on the front end of the arm section 420 exerted by shaking orthe like in a joint section on the base end side is thought to becomesmaller.

Herein, to transmit the brake release command to each motor controller200 according to a preset order and timing, it is necessary to ascertainthe completion of the brake release control in each motor controller200. In the above example, the control system 100 ascertains thecompletion of the brake release control in each motor controller 200 byreceiving a completion notification from each motor controller 200.However, the method by which the control system 100 ascertains thecompletion of the brake release control (or the brake engagementcontrol) in each motor controller 200 is not limited to such an example.

For example, after transmitting the brake release command or the brakeengagement command to the single motor controller 200, the controlsystem 100 may stand by for a predetermined time at which the brakerelease control or the brake engagement control is predicted tocomplete, treat the brake release control or the brake engagementcontrol as being complete by the elapsing of the predetermined time, andtransmit the brake release command or the brake engagement command tothe next motor controller 200 according to the preset order and timing.Alternatively, after transmitting the brake release command or the brakeengagement command to the single motor controller 200, the controlsystem 100 may acquire the measurement value of the output shaft encoder340 and the measurement value of the torque sensor 380 of the actuator300 corresponding to the motor controller 200, and after sensing on thebasis of these measurement values that the brake release control or thebrake engagement control has completed, and then transmit the brakerelease command or the brake engagement command to the next motorcontroller 200 according to the preset order and timing.

5. Experiment Results

To confirm the advantageous effects of the present disclosure, the brakerelease control according to the first embodiment described above wasactually executed in an support arm apparatus, and the amount of changein the rotational angle of the output shaft in the actuator at the timeand the driving current value of the motor (the current value given tothe motor while driving) were measured. Note that the support armapparatus used in the experiment includes an arm section configured tohave six degrees of freedom, with actuators provided in all of the jointshafts, similarly to the support arm apparatus 400 illustrated inFIG. 1. Also, the actuator provided in each joint section is an actuatorwith a built-in brake, having a configuration substantially similar tothe actuator 300 illustrated in FIG. 3.

The measurement results are illustrated in FIGS. 12 and 13. FIG. 12 is agraph illustrating change in the rotational angle of the output shaft ofthe actuator when the brake release control is executed. FIG. 13 is agraph illustrating change in the driving current of the motor of theactuator when the brake release control is executed.

FIG. 12 takes time as the horizontal axis, takes the rotational angle ofthe output shaft of the actuator measured by the output shaft encoder asthe vertical axis, and illustrates the change over time in therotational angle. Also, FIG. 13 takes time as the horizontal axis, takesthe driving current of the motor of the actuator as the vertical axis,and illustrates the change over time in the driving current. Also, bothFIGS. 12 and 13 use a dashed line to indicate the timing (time) at whichthe release of the brake of the actuator is started.

Referring to FIG. 13, it can be confirmed that, from before the releaseof the brake is started, the motor is being driven by a near-constantcurrent value, that is, the current tracking control is being conducted.Also, referring to FIG. 12, it is demonstrated that, by releasing thebrake, the rotational angle of the output shaft changes slightly, butthe amount of change is less than 0.001° and is kept extremely small.

In this way, from the results illustrated in FIGS. 12 and 13, it can beconfirmed that, by conducting the current tracking control from beforethe release of the brake is started, it is possible to effectivelysuppress angle changes in the output shaft of the actuator attendant onthe release of the brake.

6. Supplement

The preferred embodiments of the present disclosure have been describedabove with reference to the accompanying drawings, whilst the presentdisclosure is not limited to the above examples, of course. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

In addition, the effects described in the present specification aremerely illustrative and demonstrative, and not limitative. In otherwords, the technology according to the present disclosure can exhibitother effects that are evident to those skilled in the art along with orinstead of the effects based on the present specification.

For example, in the foregoing embodiment, the control target is taken tobe the arm section 420 having a configuration in which the actuators 300are provided in all of the joint sections 421 a to 421 f, but thepresent technology is not limited to such an example. For example, thebrake release control and the brake engagement control described abovemay also be applied to an arm section in which actuators is providedonly in some joint sections (also known as an arm section that includesa passive shaft). In this case, the brake release control and the brakeengagement control are executed only with respect to the joint sectionsprovided with the actuators.

Additionally, the present technology may also be configured as below.

(1)

A control apparatus configured to

execute a current tracking control on a basis of a measurement value ofa torque sensor of an actuator provided in at least one of multiplejoint sections included in an arm section of a medical support armapparatus, the current tracking control causing a motor of the actuatorto output torque by which a position and an attitude of the arm sectionare maintained, and

switch a first state in which the motor is driven in accordance with apredetermined control method, and a second state in which the jointsection is locked using a brake of the actuator.

(2)

The control apparatus according to (1), in which

the actuator is an actuator with a built-in brake, the actuator havingthe brake attached to an input shaft.

(3)

The control apparatus according to (1) or (2), in which

the actuator includes an encoder that measures a rotational angle of adrive shaft of the motor, and

the control apparatus decides a timing at which to end the currenttracking control on a basis of a measurement value of the encoder.

(4)

The control apparatus according to any one of (1) to (3), in which

the actuator includes an encoder that measures a rotational angle of adrive shaft of the motor, and

the control apparatus detects an abnormality of the motor or the brakeon a basis of a measurement value of the encoder.

(5)

The control apparatus according to (4), in which

the control apparatus detects an abnormality of the motor on a basis ofa measurement value of the encoder while the brake is being released.

(6)

The control apparatus according to (4), in which

the control apparatus detects an abnormality of the brake on a basis ofa measurement value of the encoder when the joint section is beinglocked by the brake.

(7)

The control apparatus according to any one of (3) to (6), in which theencoder is an output shaft encoder that measures a rotational angle ofan output shaft through a speed reducer of the motor.

(8)

The control apparatus according to any one of (1) to (7), in which

in the current tracking control, a current value supplied to the motorto cause the motor to output predetermined torque is computed for eachmotor by using a torque constant unique to the motor of each jointsection.

(9)

The control apparatus according to any one of (1) to (8), in which

the control apparatus executes the switching between the first state andthe second state at mutually different timings for each joint section.

(10)

The control apparatus according to (9), in which

the timing of switching between the first state and the second state foreach joint section is decided on a basis of at least one of aconfiguration of the arm section, and the position and the attitude ofthe arm section when switching states.

(11)

The control apparatus according to any one of (1) to (10), in which

a medical tool used in a medical procedure is provided on a front end ofthe arm section.

(12)

The control apparatus according to (11), in which

the medical tool is an imaging unit for imaging and performing enlargedobservation of an operative site of a patient.

(13)

A control method including:

executing a current tracking control on a basis of a measurement valueof a torque sensor of an actuator provided in at least one of multiplejoint sections included in an arm section of a medical support armapparatus, the current tracking control causing a motor of the actuatorto output torque by which a position and an attitude of the arm sectionare maintained; and

switching a first state in which the motor is driven in accordance witha predetermined control method, and a second state in which the jointsection is locked using a brake of the actuator.

(14)

A medical support arm apparatus including:

an arm section provided a medical tool on a front end; and

a control apparatus configured to control an operation of the armsection, in which

the control apparatus is configured to

-   -   execute a current tracking control on a basis of a measurement        value of a torque sensor of an actuator provided in at least one        of multiple joint sections included in the arm section, the        current tracking control causing a motor of the actuator to        output torque by which a position and an attitude of the arm        section are maintained, and    -   switch a first state in which the motor is driven in accordance        with a predetermined control method, and a second state in which        the joint section is locked using a brake of the actuator.

REFERENCE SIGNS LIST

-   100 control system-   110 user interface-   200, 200 a motor controller-   201 current value computation section-   203 motor control section-   205 brake control section-   207 abnormality detection section-   300 actuator-   310 motor-   320 speed reducer-   330 input shaft encoder-   340 output shaft encoder-   350 output shaft-   360 housing-   370 brake-   380 torque sensor-   400 support arm apparatus (observation apparatus)-   410 base section-   420 arm section-   421 a to 421 f joint section-   423 imaging unit-   430 control apparatus

1. (canceled)
 2. A control apparatus, comprising circuitry configured to obtain torque information in at least one joint of a medical articulated arm based on an attitude of the medical articulated arm, the torque information being a value of the torque necessary for maintaining the attitude of the medical articulated arm, execute a current tracking control based on the torque information in the at least one joint of the medical articulated arm, and during the current tracking control, switch between a first state in which an actuator of the at least one joint is driven in accordance with a predetermined control method and a second state in which the at least one joint is locked using a brake of the actuator.
 3. The control apparatus according to claim 2, wherein the circuitry is configured to calculate the value of the torque based on the attitude of the medical articulated arm.
 4. The control apparatus according to claim 3, wherein the circuitry is configured to calculate the value of the torque based on a configuration of the medical articulated arm.
 5. The control apparatus according to claim 4, wherein the circuitry is configured to cause a motor of the actuator to output the calculated torque.
 6. The control apparatus according to claim 2, wherein the circuitry is configured to switch the state of the medical articulated arm from the second state to the first state.
 7. The control apparatus according to claim 2, wherein the actuator is an actuator with a built-in brake, the actuator having the brake attached to an input shaft.
 8. The control apparatus according to claim 2, wherein the actuator includes an encoder that measures a rotational angle of a drive shaft of a motor, and the circuitry is configured to decide a timing at which to end the current tracking control on a basis of a measurement value of the encoder.
 9. The control apparatus according to claim 8, wherein the encoder is an output shaft encoder that measures a rotational angle of an output shaft through a speed reducer of the motor.
 10. The control apparatus according to claim 8, wherein, in the current tracking control, a current value supplied to the motor to cause the motor to output predetermined torque is computed for each motor by using a torque constant unique to the motor of each joint.
 11. The control apparatus according to claim 2, wherein the circuitry is configured to execute the switching between the first state and the second state at mutually different timings for each joint.
 12. The control apparatus according to claim 11, wherein the timing of switching between the first state and the second state for each joint is decided on a basis of at least one of a configuration of the medical articulated arm, and a position and the attitude of the arm when switching states.
 13. The control apparatus according to claim 2, wherein a medical tool used in a medical procedure is provided on a distal end of the medical articulated arm.
 14. The control apparatus according to claim 13, wherein the medical tool is an imaging device for imaging and performing enlarged observation of an operative field.
 15. A control method, comprising: obtaining torque information in at least one joint of a medical articulated arm based on an attitude of the medical articulated arm, the torque information being a value of the torque necessary for maintaining the attitude of the medical articulated arm, executing a current tracking control based on the torque information in the at least one joint of the medical articulated arm, and during the current tracking control, switching between a first state in which an actuator of the at least one joint is driven in accordance with a predetermined control method and a second state in which the at least one joint is locked using a brake of the actuator.
 16. The control method according to claim 15, further comprising calculating the value of the torque based on the attitude of the medical articulated arm.
 17. A medical support arm apparatus, comprising: a medical articulated arm to which a medical tool is to be secured; and circuitry configured to obtain torque information in at least one joint of the medical articulated arm based on an attitude of the medical articulated arm, the torque information being a value of the torque necessary for maintaining the attitude of the medical articulated arm, execute a current tracking control based on the torque information in the at least one joint of the medical articulated arm, and during the current tracking control, switch between a first state in which an actuator of the at least one joint is driven in accordance with a predetermined control method and a second state in which the at least one joint is locked using a brake of the actuator. 